1. Field of the Invention
The present invention relates to a flat lamp structure, and in particular, to a flat lamp structure having electrodes positioned on the outer wall of a gas discharge chamber.
2. Description of the Related Art
As a consequence of industrial progress, developments in mobile phones, digital cameras, digital video cameras, notebook computers, and desk-top computers are now concerned with multifunctional and aesthetic design. However, the display screen used in mobile phones, digital cameras, digital video cameras, notebook computers, and desk-top computers is an essential interactive interface. The display screen provides the user with great convenience of operation. In recent years, it has become commonplace for most mobile phones, digital cameras, digital video cameras, notebook computers, and desk-top computers to employ a LCD panel as the display screen. However, the LCD panel per se is non-luminous, and a back light module must be provided at the bottom of the LCD panel to provide a light source for displaying.
The flat lamp provides excellent luminosity and uniformity and also provides a larger surface area light source. Therefore, it is widely applied as a back light source for LCD panels and for other fields of applications. The flat lamp is a plasma luminous component, essentially utilizing the electrons emitted from the cathode to collide with the inert gas between the cathode and anode within the gas discharge chamber, and the gas is ionized and excited to form plasma. After that the excited state atoms of the plasma return to the ground state by emission of UV rays, the UV rays further excite the fluorescence substance within the flat lamp, producing visible light.
FIG. 1 is a schematic view showing the structure of a conventional flat lamp.
Referring to FIG. 1, the conventional flat lamp structure comprises a gas discharge chamber 100, a fluorescence substance 102, a discharge gas 104, electrodes 106 and dielectric layers 108. The gas discharge chamber 100 comprises a plate 100a, a second plate 100b and strip 100c mounted between the plate 100a and the plate 100b, and is connected to the edge of the plate 100a and the edge of plate 100b, forming a closed chamber.
Referring again to FIG. 1, the conventional electrode 106 is generally a silver electrode, and the electrode 106 is disposed on the plate 100a. The electrode is generally covered with the dielectric layer 108 so as to protect the electrode 106 from damaging by the collision of the ions. As shown in FIG. 1, the dielectric layer 108 covering electrode 106 is positioned at the inner wall of the gas discharge chamber 100. The gas discharge chamber 100 is charged with a gas 104. Generally, the gas 104 includes Xe, Ne and Ar, or other inert gas. Moreover, the fluorescence substance 102 is disposed on the inner wall of the gas discharge chamber 100, for example on the surface of the plate 100b, on the surface of the dielectric layer 108, and on the surface of the plate 100a not covered by the dielectric layer 108.
In the process of ignition of the flat lamp, the electrode 106 emits electrons to collide with the discharge gas 104 within the gas discharge chamber 100, and the discharge gas 104 is ionized and excited to form plasma. After that, the excited state atoms of the plasma return to the ground state by emitting UV rays, and the emitted UV rays further excite the fluorescence substance 102 within the inner wall of the gas discharge chamber 100 to produce visible light. However, on the above light luminous mechanism, the high energy ions released by the plasma generally collide through the dielectric layer, and may reach further to the electrode 106. Thus, the longevity of the flat lamp is greatly reduced.
Please note that the dielectric layer 108 covering the electrode 106 is generally fabricated by a multiple screen printing process the thickness of which is controlled between 200 μm to 250 μm. However, the fabrication process of the multiple screen printing is complicated, and the test sample capacity and yield are low. In addition, multiple screen printing can easily cause unevenness in the thickness of the film, causing each of the test samples or a single test sample with different optical characteristics of different region to differ with each other. Due to the fact that the optical characteristics of the test sample cannot be easily controlled, the designing cost for the driving circuit is increased.